Below are examples of this homework assignment from previous years. Note that these examples do not use the pdf generator, but the information requested is nonetheless the same as with the pdf generator. The first two
are examples of what we expect for homework 3 for full credit. Pay close
attention to the format and simplicity of some of the answers. Be sure to turn
in a copy of the article with the appropriate sections highlighted when you
turn in your homework and please, staple you homework before you turn it in.
The third and fourth examples illustrate what NOT to do; these assignments did
not receive high scores. Comments on these assignments are included in
capitalized letters. If you have any questions don't hesitate to e-mail us or
stop by during office hours.

The goal of this study was to evaluate a possible association between oral cancer and
antibodies to HPV in a person's blood. (Alternatively, the goal could be stated more
broadly as an attempt to identify possible causes of oral cancer by looking for
correlates.)

II. The Correlation

1. Quote:
"Those with antibodies to HPV in their blood-suggesting past exposure to
the virus-were 1.7 times more likely than others to develop oral squamous
carcinoma."

2.
First Variable: Incidence of carcinoma

3.
Second Variable: Exposure to HPV 16
antibodies

4.
Control Group: 477 healthy people of
same age and gender

5.
Treatment Group: 284 patients with oral
cancer

III. A Model that Postulates a Causal Relation Between the Two Correlated
Variables:

1. HPV causes oral cancer.

IV. A Model that Postulates that the Correlation is Caused by a Third, (or
Hidden) Variable:

One
factor the data control for: Cigarette smoking and alcohol consumption (Mark
the text where it is stated that this factor is controlled for.)

2. One factor the data do not control for:
Excessive and unprotected sex

3. A model in which this correlation is caused by
a third (or hidden) variable:

Not a good answer because it restates the
original causal model:People with HPV tend to have higher number of sex
partners and moreunprotected sex than those who don't have HPV, but unprotected
sex does not cause oral carcinoma, HPV does.

An acceptable answer: Unprotected sex exposes a person to a virus
unrelated to HPV that causes oral cancer.Unprotected sex also increases incidence of HPV, leading to the
correlation between HPV and oral cancer.

GOOD EXAMPLE 2

Article:

Title: "Study Says H.I.V. Tests Misstate
Women's Risk"

Source: New York Times

Date: November 6, 1998

I. Goal

Does gender play a role in the progression of
H.I.V. and A.I.D.S.?

II. The Correlation

1. Quote:
"Women infected with H.I.V. may be at a more advanced stage of infection
and at a higher risk of developing A.I.D.S."

2. First Variable: progression of H.I.V. to A.I.D.S.

3. Second Variable: gender - female

4. Control Group: Male drug users infected with H.I.V.

5. Treatment Group: Female drug users infected with H.I.V.

III. A Model that Postulates a Causal
Relation Between the Two Correlated Variables:

Being
a woman causes H.I.V. to progress faster than than does being a man.

IV. A Model that Postulates that the
Correlation is Caused by a Third, (Hidden) Variable:

1. One factor the data control for: Viral Load (Mark
the text where it is stated that this factor is controlled for.)

2. One factor the data do not control for: The
healthy person before infection

3. The model in which this correlation is caused
by a third (or hidden) variable:

Women receive worse health care in society so they
are weaker and H.I.V. progresses

faster because of this, not because of gender.

POOR EXAMPLE
(Grader comments are in CAPS)

Article:

Title: "Likely Cause Found for 'Phantom
Pain'."

Source: NOT GIVEN

Date: NOT GIVEN

I. Goal

To show that the brain rewires after limbs are
severed

II. The Correlation

1. Quote:
"A key portion of the brain rewires after the nerves to a limb are
severed, bring sensations from the face into receptors that once
"felt" from the arm or leg."

THIS DOESN'T STATE A CORRELATION, JUST A PROPOSED
PROCESS.

2. First Variable: brains of a group of eight monkeys remapped their sensations.

THIS IS NOT A VARIABLE.

Second
Variable: after the nerves leading
to one arm were surgically severed at the spinal cord. THIS ALSO NOT A
VARIABLE.

Control
Group: NOT GIVEN

5. Treatment Group: NOT GIVEN

III. A Model that Postulates a Causal Relation Between the Two Correlated
Variables:

Sensations are remapped if limbs are
severed.

IV. A Model that Postulates that the Correlation is Caused by a Third, (or
Hidden) Variable:

One
factor the data control for: repetition. THIS IS NOT A VARIABLE EITHER

One
factor the data do not control for: blind.

THIS ISN'T A SUFFICIENT EXPLANATION OF A LACK OF
CONTROLS.

3. The model in which this correlation is caused
by a third (or hidden) variable:

Some
Silver Spring monkeys feel sensation when limbs are severed.

THIS MODEL IS NOT DIFFERENT THAN THE
FIRST ONE GIVEN.

POOR EXAMPLE 2

Article:

Title: "Underweight Babies May Become Obese Adults"

Source: Houston Chronicle

Date: November 3, 1999

I. Goal

The purpose of the study was to find out whether underweight babies have a
better chance to

later become obese than healthy babies having normal weight

II. The Correlation

1. Quote: "underweight newborns began life
with less muscle than other babies but soon had more fat, relative to their
size"

2. First Variable: incidence of obesity

3. Second Variable: weight of newborn

4. Control Group: babies of normal weight for
their gestational age

5. Treatment Group: babies of less than normal
weight for their gestational age

III. A Model that Postulates a Causal Relation Between the Two Correlated
Variables:

Being
underweight as an infant causes obesity late in life.

IV. A Model that Postulates that the Correlation is Caused by a Third, (or
Hidden) Variable:

One
factor the data control for: weight at birth.

THIS IS NOT A FACTOR CONTROLLED; THIS IS ONE OF
THE VARIABLES INVOLVED IN THE CORRELATION.

One
factor the data do not control for: NONE GIVEN

3. The model in which this correlation is caused
by a third (orhidden) variable:

Overweight infants tend to remain heavy as they
grow up, but overweight infancy does